This invention relates to liquid spraying devices, and more particularly to paint spraying devices of the type utilizing centrifugal atomization of paint by feeding paint to a disk rotating at high speed, and thereby centrifugally distributing paint droplets off the spinning edge of the disk and onto the article to be painted.
Centrifugal sprayers are well-known in the prior art in general, and have been used in the art of paint spraying for at least about fifty years. For example, U.S. Pat. No. 2,023,710, issued Dec. 10, 1935, disclosed a centrifugal paint sprayer having a screw feed mechanism for pumping paint through an axially positioned tube, and through a passage in such tube which is controllable by a sliding gate, to a feed orifice for discharging the paint against the under-surface of a spinning disk. U.S. Pat. No. 2,251,457, issued Aug. 5, 1941, discloses a centrifugal paint sprayer having a hollow motor shaft and axial centrifugal pumping means for raising paint from a container into a spinning disk, the amount of paint being applied being controlled by an adjustable external gate which permits more or less paint emitted from the spinning disk to escape through a V-shaped gate orifice. All paint centrifugally released from the spinning disk which does not escape through the V-shaped opening is drained back into the paint container.
Almquist U.S. Pat. No. 2,749,179, issued June 5, 1956, discloses a motor-driven disk paint gun having two disks for creating an air suction to the paint receptacle. A relief passage intersects the suction passage and is coupled to the atmosphere via a hole in the gun handle, so the operator can place a finger over the hole to selectively draw paint to the disk. Kanarek U.S. Pat. No. 3,074,650, issued Jan. 22, 1963, discloses a motor-driven centrifugal disk paint gun having a screw pump paint feeding mechanism. Paint flow throught the pumping mechanism and hence to the spinning disk is controlled by a flat valve plate which is positioned at the bottom end of the screw pump, and adjustment means is provided for varying the orifice opening between the valve plate and the screw pump inlet.
U.S. Pat. No. 3,125,296, issued Mar. 17, 1964, discloses a motor-driven centrifugal disk paint sprayer having a screw pump paint feeding mechanism and a sliding gate valve metering control which controls paint flow rate by varying the opening into the pump inlet. U.S. Pat. No. 3,455,507, issued July 15, 1969 discloses a motor driven centrifugal disk paint sprayer having a screw pump and a controllable orifice between the underside of the spinning disk surface and the pump outlet tube, whereby the adjustment of this orifice permits regulation of paint flow rate.
All of the foregoing prior art patents utilize some form of paint flow rate regulation, either at the inlet of the paint pumping mechanism, or intermediate the pumping mechanism and the disk, or at the outlet of the pumping mechanism as it opens to the spinning disk surface. The present invention is an improvement in paint metering of centrifugal disk paint sprayers of the type generally disclosed in the foregoing patents, providing an efficient and economical metering mechanism for controlling paint flow rate; and providing for an accurate flow rate control.